The present invention is directed to a technique for labeling containers, and more particularly to a technique for applying decorative and/or informational labels to glass containers. Still more particularly, the invention is directed to a technique for fabricating a label composite which applies only the inks for the graphics, a method for applying the label inks to the container and a method to coat the entire container including the label to protect the inks and improve the physical characteristics and appearance of the container.
Glass containers are currently labeled in three different ways. The predominant method is printed paper labels glued to the container at the time of filling and sealing. Such labels offer almost unlimited art potential and are commonly used on food, and both returnable and non-returnable beverage containers. This is the lowest cost technique, but offers little resistance to label damage from handling and exposure to moisture or water, and may not survive the washing procedures required of a returnable container, thereby requiring re-labeling.
A second, and more recently developed, container labeling technique is that of applying a thin styrofoam label to cover the container from shoulder to heel, with the decorative and/or informational material being printed on a more dense outer skin of the styrofoam label. This is widely used on lighter-weight one-way bottles common in the beverage industry. It offers some impact resistance and a large surface area for printing product information and instructions, as well as company logos. It is, however, more costly than the paper label, has little durability, becomes easily soiled, and will not survive the alkali washing of a returnable beverage container, or the pasteurization required by some beverage containers. Also, because the printing surface is relatively rough, high definition printing is not possible.
A third container labeling technique is that of printing ceramic ink directly on the container surface using a screen printing technology. While the label appearance is generally good, the technique is typically limited to two or three colors due to cost considerations. A recent development is the preprinting of a ceramic ink decal which is then transferred to the glass container surface. This permits high definition printing and offers greater opportunities for color and art variety. Fired ceramic inks are extremely durable and will survive the alkali washing processes required of a returnable container.
However, both the direct printing ceramic ink and ceramic ink decal techniques require subsequent high temperature firing to fuse the ink to the glass substrate. In addition, while the preprinted ceramic ink label reduces the technical problems somewhat, both techniques require extreme attention to detail, a high level of maintenance and are run off-line at slow speed, with high labor costs. Due to the high cost, ceramic inks are the least commonly used labeling technique.
It is common practice in the glass container industry to treat the outer surface of the containers with materials to counteract the effects of high glass-to-glass friction experienced on freshly manufactured glass products. Glass containers are conveyed with a great deal of glass-to-glass contact and at times considerable line pressure. Without treatment there is considerable visible scratching which may result in breakage. It is common to surface treat at two locations in the operation. Immediately after forming and before lehring, the containers pass through a vapor which leaves a tin oxide film bonded to the surface. After lehring the containers are sprayed with a dilute water solution of a material which after evaporation of the water leaves a film to provide surface lubricity. Of the two treatments the tin oxide film is most costly, both for materials and system maintenance. The lubricity of the second film, though needed to prevent surface damage, may cause problems in subsequent labeling of the container.
There is an ongoing program in the container industry to reduce the weight of the container by reducing wall thickness, but still maintain acceptable product strength for both the internal pressures of carbonated beverages and the impact strength to survive handling damage in the filling operations, in the market place and by the consumer. The benefits of reduced weight are economic: lower glass melting fuel and material costs, higher container manufacturing speeds (lower cost) and reduced product shipping costs.